


My Love Is The Killing Kind

by TsukkiNoNeko



Category: Haikyuu!!, 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime)
Genre: (hm), (my agenda continues okay), (okay listen), Alternate Universe, Crossover, Demon Slayer! Akaashi, Demon Slayer! Kuroo, Feathers & Featherplay, Hypersensitive Wing Spots, Light Angst, M/M, Minor Character Death, Multiple Orgasms, Overstimulation, Smut, Trans Male Character, Trans Tsukishima Kei, Tsukigarasu | Upper Moon5! Tsukki, Wing Kink
Language: English
Status: Completed
Published: 2021-03-15
Updated: 2021-03-15
Packaged: 2021-03-22 21:00:53
Rating: Explicit
Warnings: Major Character Death
Chapters: 1
Words: 7,476
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/30044670
Author URL: https://archiveofourown.org/users/TsukkiNoNeko/pseuds/TsukkiNoNeko
Summary: “Well, I’m lost,” he sighs when he enters the village he meant to meet up with an informant at. “I don’t…”“I may be of help if you don’t mind?”The voice is lilting; it’s attention-grabbing. Tetsurou wants to listen to it for the rest of his life.Or,TJ doesn't know how to summarise so here's a two-liner.
Relationships: (implied-ish BokuAka), Kuroo Tetsurou/Tsukishima Kei
Comments: 4
Kudos: 49
Collections: Haikyuu!! NSFW Big Bang 2021





	My Love Is The Killing Kind

**Author's Note:**

> [Artist partner's work #1](https://twitter.com/nsfwooog/status/1371513380461113346?s=19) and [ #2](https://twitter.com/shrinpus/status/1371514819665408002?s=19) for the bang! Thank you Frog for working with me!
> 
> So happy to finally reveal who dies in this fic 'cause I've been 'edging' fellow HQ nsfw big bang members on that subject matter.
> 
> My thanks go to my [beta](https://archiveofourown.org/users/Amiicee_Lokei/pseuds/Amiicee_Lokei) for betaing this mess of an angsty words.

Tetsurou knows that screaming into the void won’t do shit to help with his current situation. 

He was the one who was being stupid.

He was the one who fell in love with a fucking _oni_.

It shouldn't have even begun.

He can remember it all too well.

The day his heart fell all the way to _hell_.

///

_A few weeks ago_

Tsukigarasu.

That’s the name everyone in the prefecture fears.

And that’s the oni Kuroo Tetsurou was sent to kill.

  
  


“Well, I’m lost,” he sighs when he enters the village he meant to meet up with an informant at. “I don’t…”

“I may be of help if you don’t mind?”

The voice is lilting; it’s attention-grabbing. Tetsurou wants to listen to it for the rest of his life.

“I don’t know you,” is the smartest thing that leaves his mouth.

“Do you need to know the person to get directions?” the blond stranger giggles. “Call me Kei.”

“Kuroo,” he finds himself giving his family name away. “You live alone?”

“If that’s how you find people to bed, I admire your brevity,” Kei giggles again, his moon-coloured eyes and—oh.

“You’re an oni,” his eyes are trained on the sharp fangs that are protruding. Even with the dim light, he can see it. And the _kanji_ tattooed on the pupil and iris.

“I am, yes,” Kei sighs. “I have been cursed with this… existence since I was weak enough to be turned…”

“You’re saying you _regret_ becoming an oni?”

“I’m saying I was weak as a human and listened to Muzan’s dark whispers when I didn’t need to,” Kei—Tsukigarasu—sighs again. “I just… wish I didn’t get convinced…”

“Convinced…?” Tetsurou is new to talking to oni he was sent to kill.

“Muzan… he said I’m better off as an oni than a weak human, said he would give me what I desire,” the oni looks down, his navy haori sleeves falling by his side. “I would do anything to be human again.”

“Sounds awful lot like you have an impossible wish,” the Flame Hashira chuckles. “Well, you didn’t kill me on sight, so maybe I’ll believe that you don’t wish to kill me just yet…”

“‘Just yet’, huh?” amusement colours Tsukigarasu’s words. “That’s an interesting way of saying you know you might die, Kuroo-san.”

///

Tetsurou follows Tsukigarasu—Kei?—to the central part of the village. Before he can greet his informant, Tsukigarasu is gone, a single white feather remaining where he last felt his warmth.

“You look like you just saw a ghost, Kuroo-san,” Akaashi clicks his tongue. “Are you really a Hashira?”

“I am only nineteen, Akaashi,” Tetsurou glares at his not-so-friendly comrade. “I know that you… recently lost a close comrade of yours, but—”

“Bokuto-san is none of your concern!” Akaashi yells, losing his composure. “I know… he didn’t die for nothing. That he died so we can have a future he didn’t.”

“Akaashi…”

A single tear leaves a track down Akaashi’s beautifully pale cheek before he wipes it away. Tetsurou feels bad for not knowing what to say.

“I’ve been gathering some intel for you, Kuroo-san,” Akaashi clears his throat. “It seems that the oni might be an Upper Moon.”

“That much I figured,” Tetsurou groans. 

Half an hour of bitching later, Tetsurou is released from his little chat with Akaashi. The other man whose face is impeccably stoic told him that he needs to find someone and said he could go around the village. Find some useful things for himself.

He just got offered _services_ by escorts, males and females alike, just because he looked like a foreigner. He is from the other prefecture, yes, but he wasn’t expecting—

“You sure are a popular person, aren’t you, Kuroo-san?”

The lilting voice grabs, no, _takes_ , Tetsurou’s attention at one-go. He turns around to find Tsukigarasu in his true form.

A messenger of the gods with dove-white wings in sets of three. Unfurled to their might and it’s a sight that anyone would tremble under.

But Kuroo Tetsurou isn’t an _anyone_ ; he is Kuroo Tetsurou, the Flame Hashira.

“Good to see you here, Kei,” Kuroo decides to play dumb. Pretending that he doesn’t think that Kei is an Upper Moon.

“These humans are so innocent, don’t you think?” Kei laughs, a lyrical sound at that.

“Naïve. Pure to the world’s corruption that are the oni.”

“Kei…”

“I despise this,” Kei’s eyes glow a dark shade of red, like the Hunter’s Moon. “I hate how I am no more than a beast that is caged.”

“Kei, I don’t think you’re a beast,” Tetsurou answers honestly. “You are the most beautiful person I know, Tsukigarasu… I wish you could see that.” 

“See what?” Kei’s sharp talons unsheathe as though Kuroo’s words triggered him. “I know myself better than you do, Kuroo-san. You don’t know me.”

“But I want to.”

///

The second night arrives so swiftly at the village near the forest claimed by Tsukigarasu. Tetsurou spent the day befriending some of the other slayers who were sent here before him. By ‘befriending’, he means finding their mauled bodies and making proper graves for them.

_He can’t resist his instincts, can he?_ Tetsurou muses as he finishes the last one. _That’s why he keeps killing the slayers who were sent after him._

“Kuroo-san.”

Tetsurou hears the rustling of Tsukigarasu’s feathers before he hears him. He turns around to be greeted by an ethereal sight of the pale moonlight pouring down onto Tsukigarasu.

“Tsukigarasu—”

“I told you to call me ‘Kei’,” Tsukigarasu—Kei—requests.

‘ _Kei_ ,” _but I want to call you something else_. “How about I call you ‘Tsukki’?”

“Why the sudden nickname?”

“‘Cause you remind me of the moon,” Tetsurou replies smoothly.

///

The third night is also accompanied by Tsukigarasu.

Tetsurou isn’t surprised when Tsukigarasu flies towards the window and perches on the sill.

“Kuroo-san,” Tsukki smiles beguilingly.

“Tsukki,” he replies.

“I don’t like that nickname, Kuroo-san,” Tsukki lets out a melodic giggle, slowly leaning towards Tetsurou. “I take it you have to kill me sooner or later?”

“Tsukki…”

“Don’t,” Tsukigarasu’s thumb caresses his bottom lip. “We needn’t speak of this.”

With a flurry of dove-white feathers, Tsukigarasu is gone.

///

Tetsurou used to think all the oni were the same.

That they enjoy killing humans and revel in that carnage.

It’s been a week since Tetsurou met Tsukki—Tsukigarasu. He’s been learning the soft side of the oni that’s slowly opening his heart.

He knows this is too soon to do such a thing, but these… these _feelings_ he has for the oni can’t be held back. He just knows that he can’t deny he feels _something_ for Tsukigarasu—Tsukki.

It’s unfair, Tetsurou thinks, that he has to _suffer_ just because he is still a human and Tsukki cannot undo the bad choice he made centuries ago.

“I can tell when you’re thinking of me, Kuroo-san,” Tsukki’s soft feathers tickle Tetsurou’s cheeks as they fall down upon his face before the oni tucks his wings in. “Have I really intrigued you that much?”

“You know the truth better than I,” Tetsurou grunts. “Why are you up so close to the sunrise?”

“Because sunrise is the time you usually sit by the lake and think about stuff.”

They’re currently in the little forest Tsukigarasu has claimed as his own. The lake is more of a large pond where small schools of fish swim about as the owls watch their every move.

“If owls are your favourite birds, I wouldn’t find that odd at all,” Tetsurou decides to break the awkward silence with a little comment. “‘Cause you’re nocturnal and as beautiful as the snowy owls.”

“You think I’m beautiful?” Tsukki giggles. “Gods, in my centuries of existence, so many people called me ‘pretty’, but never ‘beautiful’.”

“You’re the most beautiful person I’ve ever met, whether they be human or oni,” Tetsurou decides to be honest. “And I do want to get to know you better.”

Tsukki unfurls his wings and looks like some sort of god by doing so.

“You wish to get to know me?” Tsukki purrs, a talon pointing straight at his heart. “Would you give me your heart if I asked for it?”

“You might be a sinner, but we both know that…”

_That your innocence is mine_ , the rest of the sentence daren’t be spoken out loud, and it remains so.

“Your beauty… it is not a mask, I know this,” Tetsurou turns around to cup Tsukki’s cheek in his hand. “It’s a weapon you might have used in the past to lure people in, but I know the truth.”

“What’s the truth then, Kuroo-san?”

///

Tetsurou is plagued by the flames inside his heart.

He knows that falling for an oni is a bad idea, especially when that oni is the Upper Moon. He doesn’t know Tsukki’s exact ranking, but he can tell that the other entity can kill him so easily if he wished.

“Tsukki…” he whispers into the night air, not knowing what to do. He has always been so sure of his life. 

His mother was killed by an oni when he was merely a kid, and his father left him soon after that disaster. He was raised by an orphanage who didn’t give a damn about the kids they took in.

The former Flame Hashira caught him trying to pickpocket him. Instead of bringing him over to the authorities, the Flame Hashira fed him and told him never to do bad things again.

So far, Tetsurou has been doing a good job at _not doing bad things again_. He trained hard to become a member of the Demon Slayer Corps and fought his way towards becoming the next Hashira by securing his spot as the former’s successor.

When the Hashira grew weaker from age, he became the next Hashira with everyone’s blessing. He soon became one of the strongest Hashira the Corps has ever seen.

Now?

If anyone were to ask Tetsurou what his heart desired, he would say he doesn’t know.

He doesn't know how these feelings he has for the winged oni will develop only that it will cost him his very life if things go badly.

///

Tetsurou was putting on his summer yukata as his pyjamas when he heard the rustling of soft feathers. He peeks outside the window to see the Upper Moon oni.

“Have you heard of something called _privacy_?” he jokes, hastily fastening his yukata.

“Have you heard of being nice to me?” Tsukki giggles, and _still_ what a lyrically pleasing sound it is.

“Tsukki—”

“I know,” Tsukki presses a dainty forefinger across Tetsurou’s lips when he’s close enough. “Please don’t say it.”

“Why not?” Tetsurou wants to fight him.

“Were we to become lovers… only trouble awaits us,” Tsukki explains.

“Then we’ll battle all those troubles,” he refutes. “I will always fight for those I love.”

“Is that your way of saying you love me, Kuroo-san?”

Tsukigarasu, one of the Upper Moons perches atop the windowsill of a cheap inn Tetsurou is staying at as the night breeze caresses them both. Tetsurou leans in closer so their noses brush.

“I am vowing that I will never let you go, my beautiful Tsukki…”

“Will you die to fulfil your vow, Kuroo Tetsurou?” Tsukki asks.

“I’m willing to give up my life for you, Tsukigarasu, my beautiful Moon.”

///

It’s the tenth-night Tetsurou has been seeing Tsukki under the moonlight.

He isn’t sure yet, but the winged oni seems to be able to quasi-control the brightness of the Moon. It’s a mental note he makes for himself as he strolls his way towards the grove he likes to write poetry.

Tetsurou wasn’t given proper education, but he knows how to write a lot of kanji, and he just likes to write, that’s all. He likes how he can pour out his feelings into the poems he writes.

_Once upon a rising Moon, I met_ _  
__a man as beautiful as She—alas, our Fates_ _  
__did not align in a way that would benefit_ _  
__us both; instead, it only separated_ _  
__our very souls._

_Were it up to me, I’d make this man_ _  
__mine regardless of our circumstances;_

 _make him the one person who matters to me_ _  
__the most._

_But the happy ending_ _  
__isn’t what we vie for._

“Beautiful poem, Kuroo-san,” Tsukki slow-claps as he drops in altitude from flying. “May I ask who it’s for?”

“You know damn well who it’s for,” Kuroo wants to kiss the oni he was sent to kill.

He’s never been more tempted by anyone else this badly before.

“Soon, Kuroo-san,” Tsukki hides his lips with the sleeve-end of his yukata. “You will learn everything.”

///

Twelfth night is hard.

Literally.

Tetsurou lies awake in his futon, his cock hard from thinking about Tsukigarasu’s moon-coloured eyes and red, _red_ lips. 

Oh, what he’d do to have those strawberry-tinted lips around his aching cock.

“Tsukki…” he pants as he slips his hand under his pyjama yukata and starts stroking himself.

Tetsurou doesn’t like wearing anything underneath his yukata and never thought it’d come in handy until now. He palms himself a few times before he’s leaking down the length of his shaft. He lets out a strangled moan, thumbing at the bubbling slit before speeding up his wrist-works.

“ _Tsukki_ ,” is the last thing he says before cleaning up and falling asleep.

///

It’s been a fortnight since he’s met Tsukigarasu. And the last two weeks have been heavenly.

  
  


Tsukigarasu is harder to read than anyone else Kuroo Tetsurou had the pleasure of reading.

Holding a black stray kitten in his arms, the Upper Moon oni looks so… serene like the moonlight shining down on them. He’s watching from the distance, not wanting to disturb his… crush? Oni? Significant other?

“I can hear your heartbeat, Kuroo-san,” Tsukigarasu giggles. 

“That’s not fair for me, now is it?” Tetsurou cups the back of his head in embarrassment, walking closer to the oni. “Now, what have you got there?”

“… a cat,” his lover looks like he’s deep in thought. “I look after the stray cats sometimes. The humans are too harsh on them.”

“Are you saying _I’m_ a bad human when you’re the big scary oni?” he laughs as he wrings an arm around his crush. “C’mon, Tsukki~”

“… I told you not to call me by that name, Kuroo-san,” Tsukigarasu grouses.

Tetsurou turns the oni around and caresses half of his face in his hand as he presses their foreheads together. The oni doesn’t do anything to get free of his grasp, their haori hems brush against one another. The cat yowls from the lack of attention and jumps down onto the ground.

“Are you saying I can’t hold you like this, as well, Tsukigarasu?” Tetsurou rasps, a thin layer of air separating their lips.

“… do what you like, Kuroo-san…”

The half-moon’s glow is bright enough to make the moon-colour in Tsukki’s eyes glow in the most ethereal way. Tetsurou engraves that look of innocence and yearning in the oni’s expression before closing his own eyes.

  
  


After what feels like a century, they part, and it’s almost like they experienced something celestial. Tetsurou doesn’t know how a kiss this simple can feel so otherworldly, but he guesses that’s what happens when he’s courting an oni.

“Tsukki…” Tetsurou starts, not sure if he should continue saying it.

“I know,” is what the Upper Moon says.

“But you know how dangerous it is for both of us,” he tries to fight.

“But you’re the human between the two of us,” Tsukigarasu laughs humourlessly. “You’re the one who’s still intact with your emotions.”

“Are you saying what you feel for _me_ isn’t an emotion?” the Hashira asks.

“ _It's the closest thing to_ _an emotion I’ll ever get_ ,” Tsukigarasu sounds remorseful. “I just wish I’d met you under a different circumstance, Kuroo-san… oh, how much things would be easier if we were both humans…”

“There’s someone… a pharmacist… she’s working on a medicine that will turn an oni back to human,” he remembers just last minute. “I think you can take it.”

“I’m an Upper Moon 5, my love,” Tsukigarasu’s eyes shine a mean shade of red. “I have killed more humans than the number of the oni you’ve killed.”

“So?” Tetsurou growls. “I will vouch for you.”

Tetsurou finds it hard to make more words come out of his mouth when it’s preoccupied by his lover’s. The kiss tastes like remorse and regret, a combination he isn’t used to. He just kisses back, holding tightly onto his lover’s haori.

“I love you, Tsukigarasu,” Kuroo Tetsurou solemnly swears. “This I swear, and only death do us apart.”

///

The moon is making its full cycle to the full moon’s night when Tetsurou kisses Tsukki again. He didn’t expect this to happen again.

He thought Tsukki would reject him like the more level-headed oni he is.

“Tsukki…”

They’re currently inside a grove not so far from the mouth of the village. Anyone can see them kissing, anyone including Akaashi. The informant hasn’t shown his face since the night Tetsurou met him, which he couldn’t care less about. That meant less threat towards his relationship with the oni.

“Kuroo-san,” Tsukki pants against his lips, his arousal pressing into Kuroo’s clad thigh. “I want you, please…”

“This is dangerous,” Tetsurou curses when he feels Tsukki’s sharp fangs against his nape. “I don’t want to be eaten.”

“Then I won’t eat you,” Tsukki grins. “I get to taste you all you want without eating you.”

“Taste… me?”

Tsukki’s sharp talons aren’t for show, Tetsurou soon finds out as they slash through his kimono and bare his painfully hard cock. Tsukki doesn’t hesitate before falling to his knees and wrapping his strawberry-coloured lips around his aching cockhead, suckling hard. The Hashira bites back a curse, not wanting to strain his lover. He finds that to be a difficult task as his size seems to strain his lover’s jaw.

“You don’t have to—”

“You’re too big for me to take everything inside my mouth, Kuroo-san,” Tsukki complains as he looks up from his eyelashes. “You’re bigger than the phallic-shaped toys I tried to pleasure myself with.”

“You have toys, huh?” Tetsurou tackles his lover onto the grove floor with a light shove. “Tsukki~ I didn’t take you to be such a dirty little whore.”

“I’ve been waiting for you all my life, Kuroo-san…” Tsukki parts his yukata to show his wet sex. “Please… you’re all that I need…”

Tetsurou has never seen such a sight that is more beautiful than the moonlight shining down on his oni lover as he begs to be taken. Tsukki’s pale blond hair takes a silvery tone as his white wings look like liquid silver.

“You’re truly the most beautiful creature I had the pleasure of laying my eyes upon, Tsukigarasu,” Tetsurou states honestly before kneeling betwixt Tsukki’s thighs. 

It’s an experiment on Tetsurou’s part. He’s never been with anyone like Tsukki before, so he just goes with what _he’d_ like to be done to him and licks at the erect clit tentatively. He strokes the underside of the attentive tip, wrapping his lips around where he can. He moans as he feels his chin growing wetter from how much pleasure Tsukki is feeling. He parts Tsukki’s folds with his thumbs and licks from the bottom of the wet cleft all the way to the tip, rolling his tongue against the underside once more, garnering a helpless moan from the oni.

“Kuroo-san… _Tet-chan_!” 

“You’re making such cute sounds, Tsukki,” Tetsurou purrs against the wetness, dragging his tongue-tip around the slick-heavy entrance before finally delving his tongue inside.

Tsukki tastes better inside than he imagined. He stretches his tongue in as far as he can, spreading Tsukki’s folds farther apart. He flicks his tongue a few times before stroking the inside of his folds, taking one between his teeth and tugging gently, earning another helpless bout of moans.

“So, this is what you like,” Tetsurou purrs again, Tsukki’s pre-cum drying on his chin. “Do you want me to put my cock inside your tight cunt and fuck you raw?”

“Pl-please…” Tsukki’s eyes are welled up with tears. “I want you, Tet-chan… never wanted someone like this before…”

Tetsurou crawls up Tsukki’s body until their sexes are pressed together. His cock is fully hard from hearing just how _lewd_ Tsukki sounds while being eaten out. He rubs his cock between the slick folds a couple of times before he slides inside.

“You’re gripping too tightly, Tsukki,” Tetsurou tries to coax his lover.

“Fuck, you’re too big—” 

“You’re not as innocent as I thought you were, Tsukigarasu~” Tetsurou teases his lover. “You’re the lewdest thing I know~”

“Call me Kei, please,” Tsukki—Kei—begs. “I like that name, please… Don’t call me by what I’ve become.”

_Kei_ , Tetsurou muses inside his head, realisation dawning upon him. “Is that your human name?”

“Somehow, that’s the only thing that I can remember from my human life,” Kei confesses. “The only human part of me.”

Tetsurou starts to move once the tremors around his cock dissipate.

“You feel so good around me, Kei…” Tetsurou groans, still feeling the slight clenching from the intrusion. 

“Move before I change my mind and eat you,” Kei whispers, sounding breathless.

So he does, pulling out just a little bit just to slam back in, and repeating the motion over and over again until Kei becomes a moaning, whimpering mess underneath him. He

He dips his head down to reconnect their lips, tasting a bit of himself on the oni’s lips. The walls sheathing his cock start to tremble again, to which, Tetsurou comments,

“Does it feel that good, Kei? Am I making the Upper Moon 5 feel so good, he’s about to come again so soon?” against the cold lips.

“Just shut up and make me feel good, _Tet-chan_.”

Tetsurou grins and redoubles his thrusts, garnering even louder moans from his beloved. He knows everything he’s done so far is against the code of being a slayer, but what can he do when he’s but a slave to his own heart?

“Say my name, Kei,” he disengages their lips only to whisper in Kei’s ear. “Say my name when you come again…”

He barely started thumbing at Kei’s clit when he starts to clench around him once more, screaming out a raspy “Tetsurou!” wings fluttering like crazy. The pristine-white wings cocoon them in their grace as Tetsurou continues to thrust into the oni until he fills him up.

“I—how are you still hard?” Kei’s face reddens when Tetsurou remains inside him.

“Well… your orgasm face is just too… lewd?” he himself doesn’t know how he got hard so fast. He knows he’s got a refractory period…

Usually.

“Fuck, Tsukki, I—”

“Please don’t say it,” a dainty finger shushes him. “I know you want to say it out loud, but it’s only going to hurt us both.”

“I’m willing to leave the Demon Slayer Corps if it means I can have a future with you…” Tetsurou suggests.

“We needn’t talk about it now… I just want you, Kuroo Tetsurou…”

Tetsurou knows when to back down, so he does, physically stopping himself from talking any more than that by reclaiming Kei’s lips. He starts off with a slow rhythm of thrusting into his lover, swallowing the oni’s moans as the moonlight bathes them both.

“Kei…” he rasps just as he starts feeling Kei clenching around him again. “You’re the most beautiful thing I’ve ever had the pleasure of laying my eyes on…”

And when they come in unison, Tetsurou’s mind is tainted by remorse.

///

During the day, Tetsurou decides to find Akaashi since his informant decided to disappear from the village entirely. He finds it odd that his fellow slayer is technically missing, but he supposes he’ll just—

“Akaashi!”

Akaashi’s entire torso is covered by blood, and there’s blood trickling out of his mouth. Since it’s broad daylight, Tetsurou knows for sure it’s not an oni’s doing.

“… Kuroo-san…” Akaashi’s lips twitch up a bit. “Of course, the last person I see is the Flame Hashira who’s failed to kill the Upper Moon 5…”

“He’s too strong,” he finds himself lying. “I barely escaped with my life.”

“Don’t worry, Kuroo-san… I’m… going to die anyway,” Akaashi groans as more blood pours out of his mouth. “… if I’m lucky, I’ll be able to see Koutarou again…”

Dread overcomes Tetsurou from hearing Akaashi’s words.

“Did you take something to… end yourself?” Tetsurou asks the fellow slayer.

“There’s… I don’t think I can continue living when I can’t see Koutarou’s smile anymore… Kuroo-san… besides…” Akaashi coughs up some blood. “Dammit, my blade hurt more than I originally anticipated…”

“Akaashi, dammit, stop talking!” he takes his haori off and presses it against where the bloodstain is the darkest. “You’re a valuable member of the Corps!”

“… I lived a good life… Kuroo-san… and now I must join the only person who saw something worthwhile in me…”

The life fades away from Akaashi Keiji’s dark grey eyes and as Tatsurou closes them, he feels tears begin to form on his own. 

///

That night, Tetsurou doesn’t try to look for Kei, but the Upper Moon finds him instead. He’s still mourning for Akaashi, but the oni seems indifferent to it.

“What is it, Kei?” Tetsurou sighs, gazing into the oni’s moon-coloured eyes as he perches on the oak tree’s thick branch.

“Just wanted to see my favourite slayer tonight, that’s all,” Kei purrs out, the middle pair of his wings flapping, mayhaps in annoyance. “You reek of death, Tetsurou.”

“Maybe because someone died in my arms during the day,” he snarls at the oni. “I don’t know what you want from me.”

“Ah, your comrade died,” Kei’s eyes gleam with an understanding of sorts. “I can see why you’d be… seemingly distressed.” 

“I’m not—”

Tetsurou gets stopped by a white feather that sharpened and bars him from moving an inch. He gulps and stares at the oni.

“Were you close to that person, Tetsurou?” Kei asks. “Were you their lover?”

“No, you’ve been my only lover in recent days,” Tetsurou answers honestly. “Are you jealous, Kei?”

“I’m not jealous,” more white feathers start to surround him. “But I don’t like how you reek of another man’s scent and, whether they died or not, I don’t like it.”

“Kei…”

With one powerful stroke of the oni’s wings, the oni is right in front of Tetsurou, and their lips meet tentatively. The slayer doesn’t know whether he wants to appreciate this distraction or not.

Regardless, his body is already reacting to it and he’s just kissing the oni back enthusiastically. He moans when Kei’s talon-tips scour his torso over his shirt, and while this feels wrong… it feels so _right_.

“I want you, Tet-chan…” Kei purrs.

“Tsukigarasu…” Tetsurou whispers against the oni’s lips. “I—”

“Don’t think… you can have a bright future with me, Tet-chan…” Kei promises, lips brushing in a sensuous manner.

Not long after, Tetsurou finds his back pressed against some tree as his pants are pulled down. Akaashi’s death is already in the far, far corner of his mind as Kei’s fingertips caress and tease every inch of his cock. His tip is bubbling with the pre-cum, and when a talon-tip presses into the slit, he moans from the stimulation. 

“Kei… don’t be a tease—”

Kei’s clever tongue laps at the underside of Tetsurou’s cockhead, punching out a moan from the slayer. He lets out a low grunt when half his cock is fit inside the oni’s mouth and it feels too good.

Almost as good as being inside the oni’s folds.

“Fuck, Kei…” Tetsurou mewls out as he grips hard onto the back of Kei’s head and pushes him down, unable to control himself.

The Flame Hashira starts to thrust into the other’s mouth, feeling his cockhead hit the back of the other’s throat every so often. The way the Upper Moon would moan whenever that happens is just a plus.

When he comes down his lover’s throat, guilt surfaces from what he’s done.

“Kei, why did you—”

“I didn’t like seeing you down, Tet-chan,” a mixture of his saliva and Tetsurou’s release trickle down the corner of Kei’s lips. “If I overstepped my boundaries, I apologise.”

“There are better ways to make me feel better,” the Hashira sighs. “Like… cuddling with me.”

“‘Cuddling’?” Kei tilts his head to the side.

“Has no one cuddled with you before?” Tetsurou finds himself smiling despite the myriad of emotions clashing inside him.

“… no, I don’t believe so… but for this cuddling, I shall take you to my hideout…”

///

Maybe Tetsurou should’ve expected this ‘hideout’ to be a fucking palace when Kei, Tsukigarasu, is a fucking Upper Moon 5. The building is huge, and it looks big enough to accommodate someone winged like Kei.

The Upper Moon 5 princess-carried Tetsurou as he flew over here, landing steadily. Tetsurou isn’t necessarily afraid of heights, but that is one experience he doesn’t wish to repeat.

“This is where you hide during the day, huh?” as a Hashira, Tetsurou should behead Kei right now.

But as Kuroo Tetsurou, the foolish human in love with the Upper Moon 5, he can’t find himself to do so.

“Why, were you expecting me to be locked up in some kind of a coffin and stay there until the sun’s down?” Kei giggles. “As long as I’m safe from the sunlight, I can be anywhere, Tet-chan…”

Tetsurou allows himself to be led deeper into the building, and in the centre is the master bedroom. It’s just a black futon with pale yellow pillows.

“How does this cuddling work, Tetsurou?” Kei tilts his head to the side once more.

“Lie down first, Kei,” Tetsurou instructs.

The oni is obedient Tetsurou following suit. He wraps his arms around the oni’s slightly slimmer frame, burying his face into the crook of the other’s neck.

“I meant it when I said I love you, Kei,” Tetsurou vows. “And I will see to it so you can get the medicine that will turn you back to human…”

“I wish for it as well, Tetsurou…”

The moonlight pours down onto Kei as he sleeps, and by the time moonlight turns into sunlight, Tetsurou knows that he can’t harm this Upper Moon despite his crimes.

///

Tetsurou wonders what lies ahead of him now that he’s realised he basically betrayed the Demon Slayer Corps. As a Hashira, that’s the last thing he should be doing, but no, he’s been coupling with the Upper Moon 5, so he’s unsure about his own future.

Yes, he promised Kei he’d have the oni take the medicine once it’s finished, but he fears his ‘betrayal’ will be known amongst the slayers before then. He doesn’t know how many of his comrades would believe that the _Upper Moon 5_ is willing to become human again.

“You’re thinking awfully hard, Tet-chan,” a sleepy voice resonates from behind him. “And it’s barely sunset…”

“You’re awake?” Tetsurou turns around, only to have a kiss stolen.

“Shh… don’t think…” Kei whispers.

So, that’s exactly what Tetsurou does. He stops thinking, allowing the oni to undress him. He continues to watch as the oni discards his own clothing.

“Fuck,” Tetsurou licks at his lips when Kei spreads his legs apart and shows him his wet sex. 

“You’re the first thing I saw when I woke up, how can I not be?” Kei purrs, forefinger teasing his own clit. “I need you to sate me, Tet-chan…”

Tetsurou crawls forward until his head is level with Kei’s wet sex. As though under a trance, the Hashira licks up from the bottom of Kei’s slick cleft up to the erect tip, moaning at the taste. He starts flicking his tongue against the underside of the tip, his hands holding Kei’s thighs apart. He feels powerful like this, feeling Kei’s thighs twitch from his ministrations.

“Tet-chan, your tongue feels too good…” Kei mewls, talon-tips digging into Tetsurou’s hair. “Fuck…”

“Yeah?” Tetsurou muses, delving his tongue between Kei’s folds and feeling the wetness grow. “Mm, you taste so nice, Kei~”

“Stop— _fuck_ ,” Kei arches his back when Tetsurou finally pushes his fingers inside, curling them so he can reach his lover’s _spot_ easier.

He strokes his fingers in and out of the oni, pleased by the desperate moans escaping from Tsukigarasu’s pretty throat. He moans against the other’s wet sex, suckling hard on his clit as his fingers work themselves to draw out an orgasm.

“Serve me,” Kei whispers in a shaky voice. “Server only _me_.”

Tetsurou wishes he could answer that. He wishes he could tell Kei that he will only serve him, an oni, but he knows better than that.

Even with his divided loyalty, he knows that one day, it’s either him or Kei that will die because of whom they side with. 

“Tetsurou!” Kei screams out as he comes around Tetsurou’s fingers, walls squeezing tight around his digits.

“Need to be inside ya,” Tetsurou growls. “Can I?”

“You know you needn’t ask me,” Kei purrs out.

Tetsurou crawls up the oni’s body and strokes himself a couple of times before sliding in, face burying into Kei’s feathers. A low moan is released from how good it feels. He bites into a few of the other’s white feathers garnering the oni’s inner walls to tremble _slightly_ around his cock.

A thought flashes across his mind.

“Do you… like it when I bite your wing?” Tetsurou doesn’t know what to say. It’s not like he’s has a lot of experience fucking winged oni.

“I was hoping you’d find that out sooner than later, Tet-chan,” Kei holds his hand up to partially hide his face. “What will you do now that you’ve found out?”

Instead of biting, Tetsurou takes his lover’s feathers between his lips and nuzzles them between his lips. Kei lets out a surprised gasp from the sensation, talons digging into Tetsurou’s shoulders. He continues to nuzzle the soft feathers between his lips before starting to drag his tongue against the underside of the vanes.

Just as he starts to thrust.

“Tet-chan!” Kei gasps and Tetsurou wants to be able to see what kind of face Kei is making right now.

_Is he in absolute bliss because I’m playing with his feathers?_ Tetsurou muses to himself as he tries to play with the white feathers at the same time as moving his hips. _I wish to be the last lover you’ll ever have, Kei…_

“Feels so good, _ah!”_

Kei’s walls convulse around Tetsurou’s cock, but he isn’t done yet. Without pulling away from Kei’s wing, he slings the oni’s legs over his shoulders, but in the process, he bites down _hard_ from the slight effort it took.

Surprising Tetsurou, Kei comes from having his wing bitten.

“Fuck, you’re only drawing me closer to my own orgasm, Tsukki,” Tetsurou growls.

“Tet-chan, Tet-chan, please…”

Tetsurou doesn’t know what his lover is begging for, so he just goes back on working on the oni’s pristine-white feathers until they both finish. The wings curl around them both as Kei’s walls convulse around Tetsurou’s cock, gently caressing the slayer’s back.

“I love you, Kei,” Tetsurou reminds his lover as he pulls out. “So, so much it hurts.”

“We both know the outcome of this love story, Tetsurou,” Kei plops down onto the futon as gasps. “This is the only fate we have as a slayer and an oni…”

“You can always take the medicine once the pharmacist finishes it,” Tetsurou feels desperate. “We can have the future together if we’re both humans.”

“Is the medicine anywhere close to being finished though?” 

Tetsurou whirls on top of his lover, teeth bared, causing the oni’s wings to splay against the wooden floor.

“Why are you so set on being killed by me, Tsukki?” Tetsurou yells. “I had plenty of chances to do so, yet you’re still here, breathing right underneath me. And vice versa, too! Does that not mean you wish to become a human once more?”

“Being human means being weak once more,” Kei sighs, not resisting. “I do not wish to know weakness again.”

“You won’t be weak, Kei,” he snarls. “You’ll be Kei, the man I love.”

“Pretty words won’t make me change my mind,” Kei looks remorseful. “We’re both alive because of this thing you want to believe to be _love_.”

“Don’t you—”

“I know I have some… feelings for you…” Kei looks sad, and Tetsurou wants to kiss that sadness away as his white feathers tremble. “I was too hasty to call them _love_.”

“Kei…” 

Before Tetsurou can say anything, his lips are claimed by the Upper Moon 5, unable to utter another word.

///

Tetsurou can’t help but think that what Kei said last night holds the truth. 

_Does he actually love me or is it just lust?_ Tetsurou ponders as he takes a bath after a long day. He’s still staying at the same inn, and he wonders if…

If he knows Tsukigarasu at all. He admits that he only knows a small part of Kei—Tsukigarasu. He’s only known the man for less than a month, after all.

_To believe that an oni would actually become human for me… was I too na_ _ïve to believe that?_ Tetsurou sighs. _He said it himself…_

Tetsurou doesn’t know how to feel anymore. He feels like his love for the oni is blinding his judgement and…

“But I do love him, nothing’s going to change that,” he shakes his head as though to shake off any negative thoughts.

The Hashira picks up his blade and goes on a patrol to find some oni he could kill _instead of Kei_. 

Because his heart is keeping him from killing the one he loves.

About an hour of patrolling later, he finds a flock of winged oni.

“Turned by Tsukigarasu, I’m assuming?” Tetsurou snarls. “It’s a good thing I ran into you then…”

“Why is it a good thing, you foolish human?” one of them snickers. “You’re Tsukigarasu-sama’s little pet, aren't you?”

“Who are you calling a pet?”

In the blink of an eye, Tetsurou unsheathes his blade and kills the oni who dared to breathe.

“Who’s next in line to die?” he asks, bending his arms to hold his blade close to his face.

“You really are stupid, Kuroo Tetsurou,” this oni has a higher-pitched voice than the one he just killed. “You truly believe Tsukigarasu-sama loves you?”

“He said he feels something for me!” _Why am I arguing with these stupid clusters of feathers?_ “Why would he lie to me?”

“He’s an oni, silly human,” the onie cackles. “You can—”

Tetsurou’s sword draws a wide arc and the second oni is dead.

_Am I in denial?_

By the time Tetsurou has slain all the winged oni, the moon is high up in the night sky.

///

Unable to stomp down his doubts, Tetsurou rushes to Kei’s hideout.

“Tetsurou?” Kei looks so cute while confused.

“Hey,” Tetsurou’s heart is pounding, threatening to escape from his ribcage. “I just—”

He just claims Kei’s lips, not saying anything else. His lover kisses him back, moaning against his lips. They kiss and kiss until tears start to stream down the Hashira’s cheeks.

Kei pulls away from their kiss and kisses away those tears.

“What saddened you, Tetsurou?” Kei asks.

“Saw your minions just now,” he confesses. “Said that I’m your pet.”

“… it’s true I used to view humans as pets,” Kei admits. “But you are not my pet. I just… need more time to figure out what this _inside_ me is… what they mean in relation to _us_.”

“Prove to me that I’m not your pet, Kei…” Tetsurou never felt more vulnerable before. “Show me I’m yours as you are mine.”

Kei resumes their kiss with a soft sigh that was almost inaudible. The slight movement of Kei’s lips against his own feels like he’s being tickled. He soon feels dainty hands roaming his torso, tugging at his haori before it pools around his feet.

“Maybe I’m not wrong to call this love,” Kei begins. “Maybe an oni and a demon slayer can be lovers…”

“Kei…”

“I do feel things for you, Kuroo Tetsurou,” Kei pecks Tetsurou on the nose. “This I swear on my nonexistent soul.”

They fumble deeper into the hideout until Tetsurou’s back hits some kind of wall. He moans when his pants are undone and pulled down. Kei’s dainty fingers curl around the base of his filling cock, gracefully falling down on his knees.

It’s a pretty sight, a pretty sight Tetsurou wishes to see for as long as possible.

But he has his gut feelings that won’t be the case.

///

Of course, the happy, peaceful times don’t last forever.

Tetsurou is reading his letter, the one that demands that he cuts Tsukigarasu’s head off already. 

He burns the letter.

He doesn’t want to be a Slayer if that means he can’t be with Kei.

///

Tetsurou was sound asleep when he heard someone approaching him. He thought it was Tetsutetsutetsu, his trusty messenger raven, but something feels odd.

Whoever just entered the inn he was staying at has to be too big to be a small raven. It seems to have larger wings, to start with, and not to mention—

_Footsteps… like the oni Kei controls,_ Tetsurou notes.

Realising he needs to be out in the open, Tetsurou grabs his katana and breaks the sliding doors with an arc of his blade, promising silently to the inn owner that he’d fix it later.

Tetsurou is met with an afloat Tsukigarasu, eyes red with a killing intent, talons stained with crimson lives of humans he just murdered. All six of the Upper Moon 5’s wings are stained with the lost lives the oni took gleefully.

“Ah,” Kei—Tsukigarasu—smirks. “Thought this was going to be too easy, _Tet-chan~”_

\---

“Tsukigarasu,” Tetsurou bites back all the other words that threaten to tremble and trip over his lips.

“Kuroo,” Kei— _no, it’s Tsukigarasu_ —sounds cold, so unlike the creature he pretended to be.

“I trusted you,” anger and sorrow mix well, so easily, and it cuts Tetsurou’s heart like a knife, like Kei just walked out of his life.

_But he didn’t,_ the nasty part of his mind sneers. _He was never in your life to start with._

“I thought I could toy with another human before I ate them,” Tsukigarasu shrugs.

“Was I but a toy to you?” he can’t stop his lips from trembling.

“Aw, did my acting fool you?” Tsukki croons. “I don’t have human emotions anymore, Kuroo. That’s how it will always be until the day someone kills me.”

“I didn’t want to have to do this,” he chokes on his own breath, drawing his sword.

“I’m the Upper Moon 5,” Tsukki’s bloodstained white wings flap a few times before he’s right before Tetsurou’s eyes. “You can always have a future with me though…”

“I don’t want to betray my brethren,” _again_ , tears he didn’t know he was shedding gets wiped away by Kei’s black talons. “Please don’t make me choose…”

“That’s the fun part, Tet-chan!” Tsukigarasu giggles, his wings flapping a few times before he’s mid-air. “I love the torturous state you must be in! The fact that I wasn’t a good oni who was, indeed, ready to become human once more to start a new life with you! What a cute love story!” 

As the Flame Hashira, Tetsurou knows he has to do this. He draws a wide arc and performs the Second Style of Flame Breathing, which Tsukki dodges so easily.

“Is that the best you got, Tet-chan?” Tsukigarasu taunts, his moon-coloured eyes mocking. 

“Tsukki, I—”

_What can I say? He said that he doesn’t have human things anymore. He’s an oni, and that’s how he will live his life until the day he dies_ , Tetsurou jumps up and slashes a wide arc as he performs the First Style.

“You can do better than this, _Flame Hashira_ ,” Tsukigarasu taunts.

“You give me no choice…”

_But my heart won’t live through this, will it?_

Tetsurou keeps charging at his lover, and the oni dodges with a mocking, vicious cackle. By the time he’s tired from all the attacking, Tsukki is perching on top of an oak tree, an emotion Tetsurou can’t quite pinpoint streaking his moon-coloured eyes.

“Done yet?” he leaps down and approaches the Hashira, a sharp feather as long as his arms detach from his wings. “I didn’t think it’d be this easy…” 

“Tsukki…”

  
  


Blood-soaked feathers fly towards Tetsurou and embed themselves all over his torso and back, punching out a stream of blood from his guts.

And when Tsukigarasu’s talons pierce through his ribcage, he feels something wet and hot dropping onto his cheeks, with a whispered, _“I’m sorry, Tet-chan… maybe in your next lifetime…”_

Before everything starts to fall, fall, fall… 

**Author's Note:**

> Been 84 years since the last time I posted a KRTSK.


End file.
